This invention relates generally to infusion sets for use in connection with administration of fluids to a patient and, more particularly, the invention relates to an improved fluid manifold for use in such infusion sets.
Often in the care of a patient, it is desirable to administer medicaments of different types, simultaneously or sequentially, through a single intravenous catheter for example. This is often done by connecting various fluid reservoirs by means of flexible tubing and y-connectors to a single flexible tubing line leading to a venipuncture site in the patient. Also, preparation of a mixture of multiple medicaments in a single reservoir for subsequent infusion into a patient is sometimes done using such an infusion set.
This and other similar means of connecting various fluid sources to a single line have often been found to be cumbersome, and difficult for the medical care personnel to assemble, purge of air, and maintain. The administration of small doses of particular medicaments is inconvenient, involving manipulation of flows in the various lines and adjustment of relevant heights of the reservoirs for example, to assure proper dosage. Moreover, in certain circumstances medicaments in their respective reservoirs can become contaminated by incompatible medicaments from other reservoirs connected in the administration set due to retrograde flow.
These problems having been recognized, it was found that placing stopcocks or check valves in the fluid delivery system at critical points was useful in preventing unwanted retrograde flow and facilitating sequential fluid delivery. Also, toward the goal of streamlining the task of intravenous infusion of multiple differing fluids, manifolds for interconnection of various fluid sources have been used. Some of these manifolds incorporate check valves or stopcocks at the inlets to prevent retrograde flow. These manifolds may be used in intravenous infusion sets for direct infusion of a patient, or for mixing various medicaments into one reservoir for subsequent infusion of a patent.
In pharmacological applications, manifolds have been used to mix differing fluids in preparing various medicaments. Such manifolds have incorporated check valves preventing retrograde flow integral with, and contained within the manifold. Multiple tubing inlets convey differing fluids into the manifold in relatively high volume where they are mixed by turbulence and then exit the manifold through a single outlet.
However, the incorporation of all the various components, including check valves for example, into a single manifold in order to enable connection of multiple fluid sources has not escaped all of the problems associated with prior non-manifold devices. Many prior art manifolds include complex arrangements of tees, risers and associated valves and connectors. For example in some prior art devices, an individual check valve or stopcock is connected to each inlet riser. These external components make prior art manifolds unsuitable to be placed close to a venipuncture site (for example on a patient's arm). These prior art manifolds must be made relatively large and robust to overcome the inherent fragility of such geometrical arrangements and connections, making separate provisions for supporting the manifold necessary (for example on a stand conventionally used for hanging intravenous fluid reservoirs). Usually, elaborate provisions for protecting the manifold from damaging handling or movement would otherwise need to be made. In such arrangements, tubing lines often are confusingly branched in different directions. The necessity of providing additional support structure on an intravenous infusion hanger stand, for example, with its associated cost, and the inconvenience to medical care personnel in connecting, supporting and protecting such prior art manifolds are undesirable. These problems are especially burdensome in the case of ambulatory patients, who may need to transport the complex infusion set incorporating these features. Otherwise, some of these patients may be able to carry the infusion set about their person. For example, multiple belt-mounted syringe pumps for intravenous infusion can be used.
But on a day-to-day basis, perhaps the most problematic aspect of prior art manifolds is that the relatively large and complex manifold arrangements give rise to dead spaces within the manifold where air may be trapped or fluids may collect. This makes such devices difficult to purge, either of air, or of incompatible fluids. Also, they give rise to large switching volumes (the volume of fluid treat must be displaced through the manifold before a newly selected medicament exits the manifold).
Manifolds used in pharmacological applications also are relatively large, and thus have large switching volumes associated with them. Such devices, being intended for rapid mixing of large volumes of fluids, have considerable dead space. Turbulent mixing associated with their intended use makes such considerations relatively unimportant. However, in low (laminar) flow applications, and particularly in situations where sequential administration of fluids is desired (for example administration of incompatible fluids), the dead spaces associated with these devices makes them unsuitable. Air or fluids may linger in such dead spaces, making the manifold difficult to purge.
Many of the stopcocks used in intravenous infusion sets and associated with manifolds also inherently have dead spaces wherein fluid may collect. For example in stopcocks having a "T" passage valve body, fluid may linger in the unused branch of the "T". These problems can be critical in applications involving small doses of fluid or sequential administration of incompatible fluids.
Moreover, as mentioned above, because of the aforementioned relatively large size and external geometric complexity of the prior art manifolds with their tees, risers, check valves or stopcocks, and couplers connected in angular relationships, they are unsuited to be positioned close to a venipuncture site in a patient. Prior art manifolds are necessarily separated from a venipuncture site on a patient by a relatively long flexible tubing line, as they must be supported by some means, as discussed above. The relatively long line from the manifold to a delivery site on a patient's body inherent in prior art manifolds yields, in addition to the switching volume associated with the manifold itself, a relatively large switching volume associated with the distance a newly selected medicament must travel from the manifold to the delivery site. This later switching volume associated with the fluid tubing line also is undesirable, particularly in low volume infusion applications.
In addition to the foregoing considerations, it is undesirable for medical care personnel, who are often harried, to be confronted by a disorderly and unnecessarily complex intravenous infusion set. In addition to time wasted in setting up, purging of air and maintaining such a complex arrangement, the potential of a life-threatening mistake is increased. This is true both in direct infusion of a patient, and in hospital pharmacy settings.
Lastly, it should be borne in mind that an intravenous fluid manifold is generally disposed of after a single use. Therefore cost considerations are particularly important. Prior art devices, being relatively large and complex, also have associated with them relatively high costs of manufacture, both in terms of labor and materials. Moreover, the aforementioned time wasted by medical care personnel inherent in using complex prior art manifolds may lead to higher costs as well.
As can be appreciated from the forgoing, important considerations in using a manifold in a medical infusion set are that the infusion set should be easily set up, easily purged of air, and easily maintained in use. In such use, the manifold should be configured for efficient flushing between sequential administration of multiple fluids so that incompatible fluids do not mix. It should be reliable and rugged in the patient care environment, and have associated with it small switching volumes to facilitate the administration of very small doses of medicaments.
Hence, those concerned with the development and use of intravenous infusion sets have recognized the need for an improved fluid manifold for use in intravenous infusion sets. Such a manifold would have minimal dead space wherein fluids or air may collect. It would optimally be capable of preventing retrograde flow. Yet the manifold should be small (but not fragile) to minimize switching volumes and to facilitate placement close to a venipuncture site on a patient. Also needed is a fluid manifold that assists in the organization of the flexible tubing lines attached for a compact and orderly configuration. And lastly it is recognized that the fluid manifold must be simply and reliably constructed at low cost. The present invention fulfills these needs and others.